docs: def writeWarp(self, warpDict):
          """ Write a list of (in, out) values for a warpmap """
          warpElement = ET.Element("warp")
          axisNames = sorted(warpDict.keys())
          for name in axisNames:
              axisElement = ET.Element("axis")
              axisElement.attrib['name'] = name
              for a, b in warpDict[name]:
                  warpPt = ET.Element("map")
                  warpPt.attrib['input'] = str(a)
                  warpPt.attrib['output'] = str(b)
                  axisElement.append(warpPt)
              warpElement.append(axisElement)
          self.root.append(warpElement)